Within the scope of the present invention, an “excessive descent rate” refers to the situation wherein, during a descent, an aircraft has, at a given height with respect to the ground, a (descent) vertical speed being excessive for such a height. The aircraft is not in principle authorized to fly at such a vertical speed at this height, in particular, due to a collision risk with the ground.
As known, numerous aircrafts are provided with a collision warning device for emitting an alarm signal in the case of a collision risk of the aircraft with the ground. Regarding the warning device, it could more specifically be a device of the TAWS (“Ground Awareness and Warning System”) type, of the EGPWS (“Enhanced Ground Proximity Warning System”) type or of the GCAS (“Ground Collision Avoidance System”) type. Such a TAWS collision warning device is generally able to emit different types of alarms, being triggered on the base of different algorithms and information sources, i.e.:                alarms, being triggered mainly on the base of information supplied by a radioaltimeter on-board the aircraft. There are different categories of alarms, referred to as “Mode 1” and “independent Mode 1”, detecting all the potential collision risks for the aircraft with the ground, but being triggered on the basis of information supplied by different measurement chains. Thus, triggering the Mode 1 reactive alarm depends on the height of the aircraft above the ground, determined by the radioaltimeter of the aircraft, as well as the vertical speed of the aircraft supplied by on-board inertial systems. On the contrary, triggering the independent Mode 1 alarm depends, on the one hand, on the height of the aircraft above the ground, determined by GPS positioning system (“Global Positioning System”), as well as a ground data base giving the altitude of the ground and, on the other hand, on the vertical speed of the aircraft supplied by the GPS system; and        so-called “predictive” alarms, being triggered on the base of information contained in one or more data bases (for example, of the ground, obstacle, airport runway type, . . . ).        
When such an alarm (for a collision risk with the ground being flown over), is triggered, the crew should, in a very short time, analyze the situation, take a decision and act so as to lift up the nose of the airplane and optionally put the wings flat again.
The present invention aims at overcoming the above mentioned drawbacks. It relates to a method for automatically protecting an aircraft, including a transport airplane, for avoiding excessive descent rates.